A heat exchanger wall is, for example, present in a heat exchanger tube for spray vaporization in a plural-tube heat exchanger (compare FIG. 1). The medium to be evaporated or vaporized is, in spray vaporizers, applied or sprayed in an enclosed volume onto the tubes. The advantage is that the free space between the tubes does not need to be filled with liquid. This minimizes the amount of fill needed for such apparatus. The type of spraying must assure that the tubes are at all times sufficiently covered with liquid. In order to meet this requirement, these systems are operated with an excess amount of liquid, which is up to a factor 10 higher than the amount of liquid needed for the vaporization operation. However, the heat-transfer coefficient of the vaporization is significantly reduced by the excess liquid. To compensate for this reduction, the plural-tube heat exchanger must be oversized. The pump must be chosen of a suitable size for the circulation of the amounts of liquid needed for vaporization and for the liquid. This causes a high energy consumption by the pump, which factor is approximately 2 times the energy consumption needed when only the amount of liquid required for vaporization is conveyed.
Tubes are known from the field of absorption heat pumps, which tubes have V-shaped grooves on the outside thereof for improving the distribution of the liquid on the tube in an axial direction. Such tubes have been developed for use in expellers (brochure leaflet "F-tube" by the Firm Furukawa Electric Co., Ltd.).
The basic purpose of the invention is to provide a heat exchanger wall of the above-mentioned type in such a manner that aside from a good distribution of the liquid on its surface, good vaporization characteristics are guaranteed at the same time.